From the article: “Forty years ago, for example, Chicago’s O’Hare airport was located in a largely rural area with surrounding agriculture and relatively sparse population.”
Forty-one years ago I worked on the Illinois Tollway at the O’Hare Oasis. Walking home from work I passed by a large field of corn. No “heat island” effect from that!
The story is the same in many places around the country. Do they de-emphasize urban weather stations and emphasize rural ones? Just the opposite!
Bingo! Good answer. I believe there has also been a reduction in the number of rural data collection stations and that only increases the effect of the data from the “heat islands”.
Also, they use the data to determine global warming trends of tenths of a degree — using data that was gathered by having somebody go squint at a thermometer calibrated +/- 2 degrees and manually write down what he sees.